Highly pressurized, ultra high pure liquid carbon dioxide is required for a variety of industrial processes. For example, some of the evolving applications in the electronic industry demand the use of supercritical carbon dioxide at high flow rates and high pressures. Other applications, such as photo-resist removal, deposition, lithography, etc, require ultra high purity (UHP) liquid carbon dioxide delivered to a point of use (POU) in pressure range from 2,000 psig to 10,000 psig. The latter depends on many factors for example, specifics of an application, tool design, process philosophy, etc.
One of the methods for achieving high pressure carbon dioxide has been to pump liquid carbon dioxide to the desired delivery pressure. However, pumping liquid carbon dioxide to a high pressure can introduce impurities, such as particulates, hydrocarbons, halocarbons, etc., to the product stream.
In recently planned or developed onsite processes the amount of carbon dioxide delivered to the point of use is significant. In these cases the recycle of spent carbon dioxide from the point of use may improve the economics of the process.
There following patents are representative of processes for delivery of ultra high purity high pressure gases and liquids and recovery processes therefor.
U.S. Pat. No. 6,023,933 discloses a process which is capable of delivering ultra high purity (UHP) argon gas at pressures up to 67,000 psig for applications such as semiconductor manufacture. In the process a high purity gas is provided in a liquefied physical state, introduced to a vaporization vessel, and then, heated in an isochoric vaporizer sufficiently to vaporize the liquefied gas. As the liquid is vaporized in the isochoric vaporizer the pressure builds to the desired pressure, e.g., from 10,000 to 67,000 psig. When the liquid is substantially vaporized, another unit is used for vapor delivery.
U.S. Pat. No. 6,327,872 discloses a process for delivering liquid carbon dioxide to a point of use at pressures of 750 to 1020 psig. Their approach is to deliver liquid carbon dioxide to an accumulation vessel and then isochorically heat the liquid carbon dioxide contained therein and thereby elevate the pressure. If isochoric heating continues above the critical temperature of about 31° C., liquid carbon dioxide is converted into a supercritical fluid and liquid carbon dioxide can no longer be delivered to the point of use.
WO 03/033114 A1 and WO 03/033428 A1 disclose CO2 onsite delivery systems for multiple applications from a first carbon dioxide purification means. The purification means includes at least one means such as catalytic oxidizer, a distillation column, a phase separator or adsorption column. Multiple effluents are generated by the differing applications which effluents comprise a carbon dioxide component and a contaminant component. At least a portion of at least one effluent stream is recycled back to a first purification means which is located between the bulk CO2 storage and delivery application. The '428 disclose the use of a second carbon dioxide purification means for creating a pre-purified feed.
There is a need to create a pump free system which can deliver UHP high pressure liquid carbon dioxide at elevated pressures and achieve recovery of spent gas discharged from the point of use.